[Intel-gfx] [PATCH] drm/i915: Hold reference to intel_context over life of i915_request

[Andrzej Hajda]

References to i915_requests may be trapped by userspace inside a
sync_file or dmabuf (dma-resv) and held indefinitely across different
proceses. To counter-act the memory leaks, we try to not to keep
references from the request past their completion.
On the other side on fence release we need to know if rq->engine
is valid and points to hw engine (true for non-virtual requests).
To make it possible extra bit has been added to rq->execution_mask,
for marking virtual engines.

Fixes: bcb9aa45d5a0 ("Revert "drm/i915: Hold reference to intel_context over 
life of i915_request"")
Signed-off-by: Chris Wilson <chris.p.wil...@linux.intel.com>
Signed-off-by: Andrzej Hajda <andrzej.ha...@intel.com>
---
Hi all,

This is squash of revert of fixed patch with Chris fix for internal
branch with expanded description.

Regards
Andrzej

Signed-off-by: Andrzej Hajda <andrzej.ha...@intel.com>
---
 drivers/gpu/drm/i915/gt/intel_engine_types.h      | 1 +
 drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 1 +
 drivers/gpu/drm/i915/i915_request.c               | 7 ++-----
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h 
b/drivers/gpu/drm/i915/gt/intel_engine_types.h
index e99a6fa03d4539..a7e6775980043c 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
@@ -58,6 +58,7 @@ struct i915_perf_group;
 
 typedef u32 intel_engine_mask_t;
 #define ALL_ENGINES ((intel_engine_mask_t)~0ul)
+#define VIRTUAL_ENGINES BIT(BITS_PER_TYPE(intel_engine_mask_t) - 1)
 
 struct intel_hw_status_page {
        struct list_head timelines;
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c 
b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
index a0e3ef1c65d246..e7f748b2102263 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -5469,6 +5469,7 @@ guc_create_virtual(struct intel_engine_cs **siblings, 
unsigned int count,
        ve->base.submit_request = guc_submit_request;
 
        ve->base.flags = I915_ENGINE_IS_VIRTUAL;
+       ve->base.mask = VIRTUAL_ENGINES;
 
        intel_context_init(&ve->context, &ve->base);
 
diff --git a/drivers/gpu/drm/i915/i915_request.c 
b/drivers/gpu/drm/i915/i915_request.c
index 721e6aefec6b4d..0679863d10244f 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -134,9 +134,7 @@ static void i915_fence_release(struct dma_fence *fence)
        i915_sw_fence_fini(&rq->semaphore);
 
        /*
-        * Keep one request on each engine for reserved use under mempressure
-        * do not use with virtual engines as this really is only needed for
-        * kernel contexts.
+        * Keep one request on each engine for reserved use under mempressure.
         *
         * We do not hold a reference to the engine here and so have to be
         * very careful in what rq->engine we poke. The virtual engine is
@@ -166,8 +164,7 @@ static void i915_fence_release(struct dma_fence *fence)
         * know that if the rq->execution_mask is a single bit, rq->engine
         * can be a physical engine with the exact corresponding mask.
         */
-       if (!intel_engine_is_virtual(rq->engine) &&
-           is_power_of_2(rq->execution_mask) &&
+       if (is_power_of_2(rq->execution_mask) &&
            !cmpxchg(&rq->engine->request_pool, NULL, rq))
                return;
 
-- 
2.34.1